Manipulate organic crystal morphology and charge transport

Organic electronics has become one of the fastest developing fields with exciting advances in discovering novel organic semiconductors, enhancing charge carrier mobility, and exploring high-performance electronic device applications. Nevertheless, the solution-induced growth of small molecular organic semiconductors provokes predominant crystal misorientation, thermal cracks and grain boundary, which poses a tough challenge to maneuver the crystal alignment towards device fabrication. In this article, we conduct an in-depth review of external force-based, additive-based, and binary solvent-based techniques to effectively control the organic semiconductor crystallization, thin-film morphology, and crystal orientations. We first introduce the recent progress and the various challenges of flexible electronics, and discuss how these issues are correlated to charge carrier mobility variations. Next, we discuss the miscellaneous external force alignment methods based on the categories of slot-die coating, blade coating, substrate patterning, and air flow. Furthermore, we investigate the additive-based methods for controlling crystal growth and orientations, including polymeric additives, small molecular additives, and nanostructured additives. Finally, we discuss the binary solvent-based methods to control the crystal morphology and dimensionality. By correlating the charge transport characteristics with the intrinsic merits of those unique methods, this article shares a useful insight into maximizing the performance of organic semiconductors from a new perspective.